In X-ray diagnostic apparatuses, conventionally known is an image rendering method that renders blood flow information, which is collected by injecting a contrast material, by predetermined parameter values. Hereinafter, such an image rendering method is described as parametric imaging. In the above-described parametric imaging, a time density curve (TDC) of the contrast material is calculated for each pixel, and by using the calculated TDC, various parameter values are calculated. As for the parameter values in the parametric imaging, calculated are the time it takes to reach a peak in the TDC (time to peak (TTP)), the height of the peak (peak height (PH)), the area of the TDC (area under curve (AUC)), the arrival time of the contrast material (arrival time (AT)), the time it takes to wash out the contrast material from the peak (Wash-out), and a mean transit time (MTT), for example.
In the parametric imaging, the parameter values corresponding to the blood flow information desired by an observer are calculated for each pixel, and an image in which the respective pixels in the image are colorized by colors corresponding to the calculated parameter values is generated and displayed. This enables the observer to perform various diagnoses based on the blood flow information rendered by the displayed image. In the above-described conventional technology, however, there have been some limitations in rendering the image by the parametric imaging.